EP0937767A2 - Gas oil extender and process for its preparation - Google Patents

Abstract

Diesel fuel substitute consists of methyl esters of fatty acids with predominantly 10-24 C chain lengths. The amount of unsaturated acids present is at least 40% or 70%. E- An Independent claim is also included for the manufacture of the diesel fuel substitute comprising: (a) heating used oil or grease to 80-120o C under normal pressure optionally filtering and/or adding to a solvent, filtering and liberating from the solvent and then isolating the fatty phase; (b) heating with 2-5 times methanol under normal pressure to 50-65o C; (c) removing excess methanol and reaction water under light vacuum; and (d) distilling the reaction mixture in a vacuum or reacting the reaction mixture with 5-10 times water after cooling to the surrounding temperature, removing the ester phase and then distilling in a vacuum.

Description

The invention relates to diesel fuel substitutes and processes for their production.

Diesel fuels are flame retardant mixtures of liquid hydrocarbons, which mainly consist of paraffins with admixtures of Olefins, naphthenes and aromatic hydrocarbons exist. Diesel fuels are obtained from the distillation of petroleum from the so-called gas oil, when cracking, from tars that are in the smoldering or Hydrogenation of lignite or hard coal occur, as well as by hydrogenation of the so-called coal extract.

For some years now, the use of fatty oils, i.e. renewable Raw materials, and in particular rapeseed oil as a diesel substitute. In the meantime, rapeseed oil esters are used in smaller quantities than so-called "Biodiesel" used. Rapeseed oil consists of the triglycerides of oleic acid, Linoleic acid, linolenic acid and palmitic acid as well as a considerable Portion of erucic acid and elicose acid. The use of rapeseed oil esters as a diesel fuel, however, partial modifications to the previously customary Engines and, although it is a regenerative fuel, still relatively expensive.

On the other hand do not represent corrupt or for other reasons more usable fats and oils of animal and vegetable origin a disposal problem The so-called waste oils and fats apply in the sewage treatment plants as problematic, especially in the anaerobic environment, because these substances are poorly degradable. If only because of the high COD values if the dosage is incorrect, the biological system of the Sewage treatment plants easily, i.e. also become irreversible, overloaded. Many sewage treatment plants therefore, in principle, refuse to accept used fats or oils. As a disposal alternative biogas production has become established in recent years, can be used in fats. However, are biogas reactors in moderate climates only under certain conditions can be used and therefore provide for the disposal of waste oils and greases not an actual alternative. Waste oils and fats are therefore either stored in landfills or sent for "thermal recovery" in Oil incineration plants. On the one hand, this is costly and on the other hand means an increasing pollution of landfill areas and additional garbage.

The invention is therefore based on the object, waste oils and fats and so on to process that they can be used as a diesel substitute.

To solve this problem, substitutes are proposed which consist of the methyl esters of fatty acids with a predominant chain length of C ₁₀ to C ₂₄ , the content of unsaturated acids being at least 40%. Surprisingly, it has been found that waste oils and fats can be processed into diesel fuel substitutes, and at competitive prices, resulting in fuels that can be used with almost the same efficiency as the conventional diesel fuels without any modifications to the existing diesel engines.

Waste oils and waste fats are more vegetable and animal as starting material Origin used, such as fat from fat separators, used Fryer fats, stored edible fats, fish oils, faulty batches of nutritional fats and the like, the oils and fats inherently or through degradation mechanisms should contain about 40% unsaturated acids. In the cases in which the old fats and oils are contaminated by microorganisms, such as for example where the fats are in prolonged contact with water, such as For example, the content of the fat separator is the ester bond of the triglycerides mostly partially broken open. With increasing spoilage also form increasingly short-chain carboxylic acids such as propionic, butter and acetic acid. Depending on the storage conditions, oxidative processes can also affect the material additionally change. Waste or waste oils and fats are therefore to a very heterogeneous mixture, which is taken into account during processing is wearing.

All existing substances containing triglycerides or fatty acids with a predominant chain length between C ₁₀ to C ₂₄ can be used. Since the end product must be a liquid suitable for winter, the proportion of unsaturated acids must be at least 40 to 70% depending on the subsequent climatic application. If polyunsaturated acids are present, somewhat larger proportions of long-chain saturated acids can also be tolerated, as long as the pour point of the mixture is around 10 to -20 ° C, the desired pour point depending on the climatic conditions of the area of use or technical options such as Thermostatization of the fuel. The iodine number of the mixture should be at least 42, but preferably 80 to 115 or more. The filterability limit (pre-standard DIN V 51606) should be 0 to -30 ° C depending on the subsequent climatic application, and 0 to -20 ° C for Central Europe.

In the case of used fats and oils with a water content of over 70%, the starting material such a mixture will initially last a few hours in one Leave the phase separation tank and then the upper one Layer separated. The mixture is preferred for better phase separation with sulfuric acid, hydrochloric acid, phosphoric acid and / or ferric chloride solution acidified to a pH of about 4 to 5. The after this Procedure for separated mixtures or starting waste fats and oils with a water content of about 40 to 50% will last for several hours heated to about 60 ° C. Here there is a separation into two or more phases due to the density differences, so that the settling Sludge and water phases separated and processed separately and the fatty top layers peeled off or otherwise can be dewatered by decanting or centrifuging. Stand Suitable centrifuges are available, the mixture is heated to around 90 ° C preheated and centrifuged at this temperature. The use of Centrifuges are particularly advantageous because mostly one of accompanying substances, especially particulate, free fat obtained and most of the Water is removed. The fat blends are then under constant Stir slowly to about 120 ° C to 170 ° C at normal pressure. At Applying a slight vacuum can reduce the pressure accordingly become. This step is necessary to remove volatile components such as residual water and short chain carboxylic acids from the mixture remove. The short-chain carboxylic acids can optionally be used as condensate be won. They are then alkalized so that the water can be separated from the salts by heating. After that is with a non-volatile acid such as phosphorus or Acidified sulfuric acid so that the volatile carboxylic acids then can be obtained purely by fractionation.

When processing anhydrous greases that are contaminated with solid particles should be, these fats are at temperatures from 80 to 120 ° C heated and then filtered off from the solids. Water and particle free Used fats and oils with heterogeneous contaminants such as Protein, starch, phosphorus lipids are included depending on the type of contamination Solvents added and heated. As a solvent, those with a boiling point between 55 to 120 ° C are used, preferably Ketones, but possibly also alcohols or petroleum ether appropriate boiling point. The solvents should preferably used in anhydrous form. The optimal one The amount of solvent depends on the type of fat and on Degree of pollution. In general, the amount of solvent is three to five times the amount of fat used and should be selected so that at the beginning of the warming a clear solution next to the undissolved sediment results. The sediment is then filtered in the heat is removed and the solvents are removed by distillation and can be used again.

These triglyceride and / or fatty acid mixtures prepared in this way are then preferably an analysis to determine the contained Subjected to fatty acids, so if necessary before further processing by distillation already too high a proportion of long-chain saturated fatty acids removed can be. For this purpose, the fat mixtures are as low as possible Amounts of acetone or other ketone with a boiling point below 120 ° C in the heat just cleared and then below 20 ° C, preferably cooled to about -10 ° C. Divide from the previously clear solution then fatty acids or triglycerides of the long-chain saturated acids and can be removed by filtration. The exact amount of tolerable long-chain fatty acids with a saturated character depends on the individual characteristics of the fatty acid spectrum and, if necessary, must Creation of larger ester batches can be determined experimentally.

The cleaned and if necessary by cooling and filtration of part of the Long-chain acids freed crude fat is then two to five times Amount of anhydrous methanol is added, and preferably an acid catalyst such as 1 to 2% by weight of sulfuric acid in concentrated form, based on the amount of fat added. This reaction mixture is then a few hours, usually 12 to 15 hours at 20 to 30 ° C or on Temperatures between about 50 to 65 ° C heated under reflux. At For example, a reaction time of from 60 to 64 ° C is sufficient 1 to 3 h. The completeness of the esterification or transesterification is in appropriately controlled analytically. The reaction can, if necessary Addition of water-binding agents such as dry molecular sieves, Silica gels, highly concentrated sulfuric acid etc. accelerated or to be completed.

After the esterification reaction has ended, the mixture can be prepared in two different ways Because of being worked up, namely either by adding of equimolar amounts of non-aqueous or aqueous base for neutralization the catalyst acid, followed by excess methanol and the water of reaction at normal pressure or in a slight vacuum by distillation be removed. With a vacuum between about 250 to 50 mm Hg keep the temperature as low as possible during the distillation. The Reverse reaction can be largely suppressed in this way. The The crude ester mixture is then preferably freed from the salt by filtration and then in a conventional manner at a vacuum of about 10 to 1 mm Hg distilled or rectified. If the salt is not in front of the Removed distillation, it remains in the sump.

If the fat mixture still contained triglycerides or as a starting material Triglycerides are used as an additional by-product glycerin obtained as a distillation residue.

The crude ester mixture can also be used after cooling with the five to added ten times the amount of water and under pH control until Reaching the neutral point can be neutralized with dilute lye. After stirring is complete on the methanol, water and if necessary, the glycerol phase of the crude ester and can be deducted. The rawest is then distilled or rectified as indicated above.

The water-methanol mixture obtained during the work-up with low Portions of ester are separated by distillation and processed again fed.

If desired and not yet done, you can also go to the current one Time from the methyl ester mixture still the esters with long-chain saturated carboxylic acids are removed by mixing either is stored cool or by placing them in the heat in as little as possible Alcohol or ketone dissolves and then cools down, making it relatively difficult Separate soluble palmitic and stearic acid methyl ester and then filter off can be.

Depending on the requirements, either certain are defined as diesel fuel Sections of the ester mixture are used or it can be rectified after rectification also mixtures with certain compositions and thus accordingly influenceable properties are produced. For winter suitability of fuel, the pour point must be at about 10 down to -20 ° C. If the ester mixture has a high proportion of multiple Has unsaturated acids, the proportion of saturated long-chain Acids be relatively high. If oleic acid predominates and its proportion below 50%, the long-chain acids may need to be removed as described become. The limit of filterability can also be adjusted accordingly yes can be set as required.

Field trials have shown that they are now in use Diesel engines with these ester mixtures obtained from used fats and oils work fine. The esters have rapeseed oil esters comparable physical and chemical properties with regard to the density in the range of about 0.90 and an iodine number that is at least 40, but preferably up to 115 or above. The iodine number increases with a correspondingly higher content of polyunsaturated acids.

The invention is explained in more detail below using an example:

Example:

Waste grease from industrial grease traps is put into one after delivery Settling tank introduced and mixed vigorously. The water content of the Mixture is about 70% by weight. To set the pH to 4 acidify the mixture to this value with sulfuric acid. After this Mixing will stand overnight for phase separation calmly. It is advantageous if the settling tank has a cooling facility is equipped to be as good and as possible even in the warmer season to achieve rapid phase separation. In the colder season that is enough Ambient temperature for sufficient cooling.

After the fat layer has settled, it is separated using a scraper. The aqueous phase is drawn off and disposed of separately.

The fat mass that is still water in amounts of about 30 to 60% by weight contains, is now in a reactor with constant stirring Normal pressure slowly to 60 ° C to 90 ° C, with some of the water itself settles down and can be removed, and then heated to 120 ° C. The water still contained and volatile acids escaping, which may collected with the help of lye in a gas scrubber and processed further can be. The mass is about an hour at the specified Leave temperature and then still hot filtered to particulate Remove impurities.

The fat mass is then stirred with three times the amount of methanol moved and solved. The solution becomes more concentrated after the addition of 1% by weight Sulfuric acid, based on the amount of fat, under normal pressure three Heated at a temperature of 50 to 65 ° C under reflux. After two and three hours the composition of the solution analytically controlled by DC, GC or HPLC and the fatty acid or Ester spectrum determined. Possibly. can by adding water-binding Agents such as dry molecular sieves or silica gels in amounts of about 3 to 5% the reaction is accelerated or completed.

After completion of the esterification, the solution becomes neutralization the catalyst acid with an equimolar amount of sodium bicarbonate Stir decomposes. The solution is then created using a Vacuum of about 250 mm Hg of excess methanol and water of reaction exempted. The temperature should preferably not exceed 50 ° C to keep the back reaction as low as possible.

The crude ester mixture is then filtered off from the fat-insoluble formed Freed sodium sulfate and transferred to a vacuum distillation system. The distillation or rectification then takes place at a negative pressure of about 1 up to 10 mm Hg.

The distillation sump consists of very small proportions of high-boiling Fatty acids or their esters and glycerin, which can be processed separately on request can be.

The distillation cuts of the esters are made in the smallest possible quantities Dissolved methanol and cooled. After separation of the palmitic and / or stearic acid methyl ester these are filtered off and the solvent in Vacuum removed by distillation.

The ester cuts are oily, somewhat yellowish liquids with completely neutral Odor.

Claims (16)

Diesel fuel substitute, consisting of the methyl esters of fatty acids with a predominant chain length of C ₁₀ to C ₂₄ , the content of unsaturated acids being at least 40%. Diesel fuel substitute, consisting of the methyl esters of fatty acids with a predominant chain length of C ₁₀ to C ₂₄ , the content of unsaturated acids being at least 70%. Diesel fuel substitute according to claim 1 or 2, characterized in that the pour point of the mixture is between 10 to -20 ° C. Diesel fuel substitute according to claim 1 or 2, characterized in that the iodine number is at least 42 and preferably about 115 is. Diesel fuel substitute according to claim 1 or 2, characterized in that the filterability limit is between about 0 to -30 ° C lies. Process for the production of diesel fuel substitutes from waste oils and fats, characterized in that a) the oil or fat, if necessary after previous sedimentation with a high water content, heated to about 80 to 120 ° C. under normal pressure, optionally filtered and / or taken up with a solvent, filtered and freed from the solvent and the fat phase isolated, b) heated to about 50 to 65 ° C. with about two to five times the amount of methanol under normal pressure, c) then separated from the excess methanol and water of reaction under a slight vacuum d) and the reaction mixture is then distilled or rectified in vacuo. Process for the production of diesel power substitutes from waste oils and fats, characterized in that a) the oil or fat, if necessary after previous sedimentation with a high water content, heated to about 80 to 120 ° C. under normal pressure, if necessary filtered and / or taken up with a solvent, filtered and freed from the solvent and the fat phase isolated, b) heated to about 50 to 65 ° C. under normal pressure with about two to five times the amount of methanol, c) then separated from the excess methanol and water of reaction under a slight vacuum d) and after cooling to ambient temperature, the reaction mixture is mixed with five to ten times the amount of water, the ester phase is stripped off and this is then distilled or rectified in vacuo. A method according to claim 6 or 7, characterized in that in Step b) an acid catalyst is used. A method according to claim 6 to 8, characterized in that as Catalyst sulfuric acid is used. Process according to Claims 6 to 9, characterized in that in Step c) under negative pressure, preferably about 250 to 50 mm Hg negative pressure is worked. .Procedure according to claim 6 to 10, characterized in that in Step d) is carried out at about 10 to 1 mm Hg negative pressure. A method according to claim 6 to 11, characterized in that the acid catalyst is removed after completion of the esterification. A method according to claim 6 to 12, characterized in that in Step a) as solvent those with a boiling point between about 55 to 120 ° C can be used. Method according to claims 6 to 13, characterized in that Ketones are used. A method according to claim 6 to 14, characterized in that before Step b) or after step d) of the process, part of the saturated long-chain acids or esters is separated. A method according to claim 6 to 15, characterized in that the Separation with or without the addition of small amounts of solvents by cooling the mixture and removing the esters precipitated he follows.